The present invention relates to universal joints and to connection assemblies between a yoke and the shafts of a universal joint cross member.
Modern vehicles are often equipped with universal joints that comprise a cross member having four shafts or trunnions. Bearings are mounted on each shaft, and two yokes are mounted onto opposed pairs of shafts. The yokes are mounted at positions spaced 90xc2x0 relative to each other and are each connected to drive shafts. This arrangement allows rotation to be transmitted through varying angles between the drive shafts, through varying angles. This type of universal joint is particularly popular in heavy. duty vehicles such as trucks.
Universal joint assemblies experience a great deal of stress and vibration and are exposed to a hostile environment on the underside of a vehicle. Thus, the connection between the yoke and the bearings should be secure and stable. Proper functioning of a universal joint also requires adequate lubrication between the bearings and the shafts. The universal joint designs utilized in the past have not always achieved these goals for yoke and cross member connections.
Conventionally, universal joints have utilized yokes that have full circular or cylindrical bores to receive a bearing and shaft. The full circular bore surrounds and supports the bearing during operation of the universal joint. Typically, the two shafts on the cross member are inserted within the bores in the yoke. The bearings are then inserted radially inwardly through the outer end of the bore and onto the shafts.
One problem with this arrangement is that since the bearings are inserted through the bores in the yoke after insertion of the shafts, the universal joint manufacturer has been unable to finally mount the bearings on the cross member shafts. Rather, the bearings must be mounted on the shaft at the vehicle assembly line. Typically, the assemblers at the vehicle assembly line are not as skilled in proper lubrication or assembly of universal joint bearings as assemblers at the universal joint manufacturer. For that reason, there has sometimes been improper lubrication or assembly of universal joints assembled on the assembly line.
To address this problem, universal joints have been developed wherein the cross member may be preassembled with its bearings already attached. In one prior art universal joint, the cross member shaft and bearing lay in a half-circle bore in the yoke. Metal straps surround the bearing and are connected to the yoke with bolts. This prior art assembly requires tight dimensional control.
In another prior art design, the bearing is connected to the yoke with bolts. The mounting bolts in this universal joint connection may become loose due to the high force moments. With either type of assembly, small locators on the bearing may be used to transmit rotation between the bearing and yoke. The small locators are placed relatively far from the centerline of the shaft. The locator provides a good deal of the reaction surface for torque transmission, and the distance from the shaft centerline results in relatively high force moments.
In a disclosed embodiment of the present invention, wing bearings support two shafts of a cross member and are bolted to a yoke. The yoke includes two opposed brackets, each having two arms forming a part-circular surface to receive the wing bearing and cross member shaft. The arms extend around more than 90xc2x0 of the bearing""s outer periphery to provide a secure engagement between the yoke and bearing. The bearing includes a depression on an outer wall of the bearing cup. The yoke bracket includes a locator finger extending between the arms of the yoke bracket, and located in the bearing depression. Preferably, the fingers extend radially inwardly to overlay the needle bearings, and at least a portion of the shaft is received in the wing bearing. The extension places the finger relatively close to the center axis of the shaft, minimizing the moment.
In another feature of the invention, the wing bearing includes a shoulder projecting from the periphery of the bearing. A yoke receiving the bearing has a mating surface disposed between the bracket arms. The shoulder contacts the mating surface to provide a secure connection between the bearing and the yoke, and inhibit rotation of the bearing in the yoke. In a preferred embodiment, the yoke also includes a lip extending beyond the mating surface, and between the bracket arms to overlay a top portion of the shoulder.
The inventive universal joint preferably combines one yoke having the prior art full circular bore mounting two shafts and a second yoke utilizing the above-described wing bearings which are bolted to the yoke. The universal joint manufacturer may preassemble a yoke having full circular bores onto two of the shafts of the cross member with its associated bearings. In this way, the universal joint manufacturer is able to insure proper lubrication of those bearings. The universal joint manufacturer may then mount the wing bearings onto the other two shafts of the cross member. The yoke and assembled cross member may then be shipped to the vehicle manufacturer. When the vehicle manufacturer assembles the drive line of the vehicle, the assembler at the vehicle assembly line need only bolt the wing bearings to a second yoke. Thus, the benefits of the full circular bore are obtained for two of the shafts, and the benefits of utilizing a wing bearing are obtained for the other two shafts.
In a method of assembling a universal joint utilizing the present invention, the universal joint assembler mounts a conventional first yoke having full circular bores onto two of the shafts. Wing bearings are mounted on the other two shafts. That assembled yoke is then transported to the vehicle assembler. The vehicle assembler assembles the drive line to include the first yoke, and bolts the wing bearings onto a second yoke. In this way, the assembler at the vehicle assembly line is not required to provide any lubrication for the bearings.
With this inventive solution, applicant has developed universal joints that require no maintenance lubrication. By insuring the proper lubrication is provided at the initial assembly, no routine lubrication maintenance is required. Thus, once assembled, the universal joint will be permanently lubricated for its expected life.